1. A remnant or trace of an organism of a past geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth's crust.
2. One, such as a rigid theory, that is outdated or antiquated.
3. Linguistics.
   1. A word or morpheme that is used only in certain restricted contexts, as kempt in unkempt, but is otherwise obsolete.
   2. An archaic syntactic rule or pattern used only in idioms, as so be it.

1. Characteristic of or having the nature of a fossil.
2. Being or similar to a fossil.
3. Belonging to the past; antiquated.

[From Latin fossilis, dug up, from fossus, past participle of fodere, to dig.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.